Signalling Control for a Point-To-Multipoint Content Transmission Network

ABSTRACT

The invention relates to a technique for controlling a signalling for a point-to-multipoint (PTM) content transmission in a PTM-enabled network environment. A method embodiment of the invention comprises the steps of transmitting signalling information related to a PTM content transmission along a downstream signalling distribution tree (MSG) to a plurality of network access nodes; and receiving, in response to the signalling information, an aggregated feedback report from a feedback aggregation server separate from the downstream signalling distribution tree, wherein the aggregated feedback report is indicative of feedback reports from the plurality of network access nodes related to the signalling information.

FIELD OF THE INVENTION

The invention generally relates to the field of point-to-multipointcontent transmissions in a network environment, and in particular in amobile network. More specifically, the invention relates to a techniquefor controlling a signalling for a point-to-multipoint contenttransmission.

BACKGROUND OF THE INVENTION

Telephony and on-demand streaming services are examples forPoint-to-Point (PTP) or unicast communication services. Broadcast andmulticast services, on the other hand, are based on Point-To-Multipoint(PTM) communication. Using a PTM communication, content (such as voice,text, graphics or multimedia data) is transmitted from typically asingle source to multiple destinations. PTM services might for examplebe streaming services or file delivery services.

The 3GPP (3^(rd)-Generation Partnership Project) has specified broadcastand multicast services for GSM (Global System for Mobile Communications)and UMTS (Universal Mobile Telecommunications System) networks, namelythe Multimedia Broadcast and Multicast Service (MBMS) feature. Thisfeature is documented for example in the 3GPP TS (TechnicalSpecification) 23.246 and in TS 26.346. MBMS adds a plurality ofbroadcast/multicast-related techniques to conventional GSM or UMTSnetworks. For controlling these techniques, a dedicated MBMS controlnode is specified, which is called the broadcast/multicast servicecentre (BM-SC). Within MBMS, the BM-SC is responsible for providing anddelivering broadcast/multicast services.

Downstream of the BM-SC, each node in the network has a list of furtherdownstream nodes to determine to which nodes it should forward MBMScontent. Thus, a hierarchically organized content distribution tree iscreated wherein the network access nodes serving a single radio cellform the leaves of the distribution tree. For instance in a GSM network,a base transceiver station (BTS) of a base station subsystem may form anetwork access node. In an UMTS network, the Node B stations in theradio access network may form the network access nodes.

The BM-SC serves as an entry point for content delivery, sets up andcontrols MBMS transport bearers, and initiates MBMS transmissions. Forexample, the BM-SC may provide the service announcements that signal anupcoming multicast transmission to the user equipment (UE) being memberof the related group. These announcements include all necessaryinformation such as multicast service identifier, Internet Protocol (IP)multicast addresses, time of transmission, and media descriptions that auser equipment needs to join a multicast session. Further signalling maybe related to the actual start of a PTM content transmission, or“session”, to the session stop or to a session update.

The MBMS-related signalling is transported over PTP connections. Forexample, in a UMTS network, a GGSN (Gateway GPRS Support Node) acting asan edge gateway for the PTM content transmission may replicate asignalling message received from the BM-SC for all connected SGSNs(Serving GPRS Support Nodes), which further replicate the message to allconnected RNCs (Radio Network Controllers)/BSCs (Base StationControllers). In the upcoming UMTS LTE (Long Term Evolution) networks,presumably the BM-SC and/or an edge gateway (called access gatewaywithin the LTE framework, e.g., an evolved GGSN) have to directlycommunicate signalling information with the network access nodes (e.g.,evolved NodeBs). In any case, a potentially large number (e.g., severalthousands) of signalling messages have to be constructed and transmittedby using the same number of unicast signalling connections. Inparticular in case of LTE, massive message replication and connectionsetup results in a significant processing delay between the first andthe last of the signalling messages to be replicated.

A reliable PTM content transmission service requires that the networkaccess nodes acknowledge reception of the PTM signalling by sending afeedback information to the PTM control node, i.e. the BM-SC and/or theedge gateway. However, transmission of feedback messages along the PTMdistribution path via PTP messages loads the interconnecting links andnodes. The load is even increased if, for example, a feedback message ismissing from one or more network access nodes. The PTM control node maythen have to repeat the signalling transmission at least towards thesenetwork access nodes. The processing of a large number of feedbackmessages at the PTM control node leads to a further processing delay.

WO 03/094534 A2 describes a network environment enabled for multi-usermultimedia messaging services. A multimedia message is distributed froman originator server to multiple recipients via one or more recipientservers, which execute a multicast delivery to the receiving userdevices. The recipient server receives status messages from the userdevices, each status message comprising an indication of a transmissionstate of the multimedia message at one of the user devices. Therecipient server acts to aggregate the status indications into a reportand sends the report to the originator server.

There is a need for an improved technique for PTM content transmissionsignalling in a PTM-enabled network environment.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a method for controllingPTM content transmissions in a PTM-enabled network environment isproposed. The method comprises the steps of transmitting signallinginformation related to a PTM content transmission along a downstreamsignalling distribution tree to a plurality of network access nodes; andreceiving, in response to the signalling information, an aggregatedfeedback report from a feedback aggregation server separate from thedownstream signalling distribution tree, wherein the aggregated feedbackreport is indicative of feedback reports from the plurality of networkaccess nodes related to the signalling information. The method may beperformed in a PTM control node, for example a BM-SC and/or an edgegateway of the network.

The signalling information may comprise any information related tocontrolling a PTM content transmission. For example, the signallinginformation may comprise any information which is or may be included ina signalling message for controlling a PTM content transmission. In oneimplementation of the invention, the signalling information may indicateat least one feedback aggregation server. For example, the signallinginformation may comprise a list of aggregation servers. The signallinginformation may indicate a dedicated address of one or each feedbackaggregation server. The receiving network access nodes may then use theaddress(es) to determine the aggregation server to which they directtheir feedback. An address may for example be provided as an IP addressor as a logical reference, e.g. a host name to be resolved via a DNS(Domain Name System).

The address may also be a multicast or anycast address, for example anIP multicast address, associated with multiple aggregation servers, ormay be a logical reference which is resolved via DNS to one or moremulticast addresses. The multicast address may be used by a PTM controlnode for signalling related to multiple PTM content transmissions. Forexample, in a network a single (“joint”) multicast address pointingtowards a sub-network of aggregation servers may be used. Routingmechanisms may be implemented for routing of the multicast traffic (thefeedback reports transmitted from the network access nodes towards theaggregation server sub-network) to meet traffic management conditionsrelated to, e.g., load balancing. The multiple aggregation servers mayform a server pool. The pool may comprise all or some aggregationservers of a network.

In one mode of the invention, the method comprises the further step ofrepeating, based on an evaluation of the received aggregated feedbackreport, the transmission of the signalling information. For example, thePTM control node may determine from the received aggregated feedbackinformation one or more network access nodes which do not have receivedthe signalling information. The repeated transmission may be performedbased on a PTP service of the network environment, for example in casesin which only few network access nodes missed the first signallingtransmission.

In one implementation of the invention, the signalling informationcomprises a feedback request indication such as a flag acting as anindicator. The feedback request indication may explicitly command anetwork access node to send or to refrain from sending a feedback.

In some variants of the invention, the signalling information istransmitted using a PTM service of the network environment. Thesignalling distribution tree may thus be based on the PTM service (or asmall number of PTM services) instead of a potentially large number ofunicast connections. For example, the access nodes may be members of oneor more MBMS multicast groups configured specifically for the transportof signalling information.

According to a second aspect of the invention, a method of operating anetwork access node for handling point-to-multipoint (PTM) contenttransmissions in a PTM-enabled network environment is proposed. Themethod comprises the steps of receiving signalling information relatedto a PTM content transmission from a PTM control node, wherein thesignalling information is received along a downstream signallingdistribution tree; determining a feedback aggregation server separatefrom the downstream signalling distribution tree; and transmitting afeedback report related to the signalling information to the feedbackaggregation server.

The network access nodes may be responsible for granting user terminalsaccess to the network and may eventually deliver the content towardsthese terminals. The network access node may for example be implementedas a base transceiver station in a GSM network, a NodeB in an UMTSnetwork, or an evolved NodeB in an UMTS LTE network.

According to one variant of the invention, the method comprises the stepof determining the feedback aggregation server from the signallinginformation. For example, an address of the server or an address listcomprising several servers may be included in a signalling message. Inone representation of the invention, the signalling informationindicates a multicast address associated with multiple feedbackaggregation servers and the feedback report is transmitted using themulticast address.

Additionally or alternatively, the method may comprise the step ofdetermining the address of the feedback aggregation server from adefault list of feedback aggregation servers. An address of the feedbackaggregation server may be different from an address of the PTM controlnode. For example, the feedback aggregation server may be a dedicatednode or may be co-located with another network node, e.g. anothernetwork access node.

The feedback report may comprise at least one of an acknowledgement ofreceived signalling information, an indication of a result of a processtriggered by the received signalling information and status informationrelated to the PTM content transmission. As an example, the receivedsignalling may trigger the (re-)allocation of resources for the PTMcontent transmission. An indication of successful allocation may then beincluded in the feedback report. As another example, the network accessnode may provide a feedback indicating the reception of signallinginformation and may provide at later times further feedback informationon a periodical basis indicating, e.g., a resource usage.

In one implementation of the invention, the step of determining thefeedback aggregation server comprises selecting one server from a listof feedback aggregation servers. In one implementation of the invention,several addresses related to one or more access nodes may be availableto the network access node, for example from the received signallinginformation as well as from a default list and possibly other sources. Adecision algorithm has then to be implemented on the access node todecide which of the addresses shall be used. For example, a randomselection may be performed.

In one implementation of the invention, the signalling information isreceived based on a first PTM service of the network environment. Asecond PTM service may then be used for conveying the PTM contenttransmission. The method may comprise the further step of identifying,based on a service identifier indicated by the received signallinginformation, the second PTM service of the network environment for thePTM content transmission.

According to a third aspect of the invention, a method of operating afeedback aggregation server in a PTM-enabled network environment isproposed, in which signalling information related to a PTM contenttransmission is transmitted from a PTM control node along a downstreamsignalling distribution tree to a plurality of network access nodes. Themethod may comprise the steps of receiving feedback reports responsiveto the signalling information from a plurality of senders; aggregatingthe received feedback reports into an aggregated feedback report; andtransmitting the aggregated feedback report; wherein the feedbackaggregation server is separate from the downstream signallingdistribution tree.

The plurality of senders may comprise at least one of one or more of theplurality of network access nodes and one or more lower-level feedbackaggregation servers (or both). The feedback reports may comprise one ormore feedback messages, e.g. acknowledgment messages, from the networkaccess nodes or may comprise aggregated feedback reports from thelower-level aggregation servers. The feedback information mayaccordingly be received directly from the network access nodes or fromother aggregation servers.

The aggregated feedback information may be transmitted towards the PTMcontrol node. This may comprise sending the aggregated feedbackinformation directly to the PTM control node, or may comprise sendingthe aggregated feedback information to a higher-level aggregationserver.

One mode of the invention comprises the further step of receiving anindication of at least one of the PTM control node and a higher-levelfeedback aggregation server as a destination for the aggregated feedbackreport. In one variant of the invention, the indication may comprise anindication of a multicast address associated with multiple higher-levelfeedback aggregation servers. The indication may be received via anadministrative intervention, or may be received in the form of asignalling information, e.g. from the PTM control node. As an example,the PTM control node may be indicated by the feedback reports receivedfrom the plurality of senders.

In one implementation of the invention, a list of higher-level feedbackaggregation servers may be provided to the server, for example byadministration or via signalling. The method may then comprise the stepof selecting one server from the list of higher-level feedbackaggregation servers. The selection may comprise to randomly choose ahigher-level server. Additionally or alternatively, a differentalgorithm may be applied, which for example ensures load-balancingbetween the higher-level aggregation servers.

In some implementations of the invention, the method may comprise thefurther step of receiving assignment information indicating anassignment of an aggregation server functionality to the receiving node.Triggered by the reception of the assignment information, the receivingnode may then locally instantiate the feedback aggregation server. Sucha dynamic assignment of the role of a feedback aggregation server may besuitable, for example, in networks in which at least some of thefeedback aggregation servers are co-located with other network nodes,e.g. network access nodes. The assignment information may be includedwithin signalling information related to a particular PTM contenttransmission; for example, the signalling information may additionallyindicate an MBMS session announcement or session start to a networkaccess node.

In one representation of the invention, the aggregated feedbackinformation may be transmitted at predetermined time intervals and/orafter a predetermined number of feedback messages have been received.For example, the aggregation server may collect feedback reports frommultiple network access nodes for a time interval of 10 seconds and maythen transmit an aggregated feedback report towards the PTM controlnode.

According to a further aspect of the invention, a computer programproduct is proposed, which comprises program code portions forperforming the steps of any one of the method aspects of the inventiondescribed herein when the computer program product is executed on one ormore computing devices, for example on an aggregation server, a PTMcontrol node or a network access node, such as a BTS or NodeB of amobile network. The computer program product may be stored on a computerreadable recording medium, such as a CD-ROM or DVD. Additionally oralternatively, the computer program product may be provided for downloadby a download server. The downloading may be achieved, for example, viathe Internet.

According to a further aspect of the invention, a PTM control node isproposed, which is adapted for controlling PTM content transmissions ina PTM-enabled network environment. The the PTM control node comprises atransmission component adapted for transmitting signalling informationrelated to a PTM content transmission along a downstream signallingdistribution tree to a plurality of network access nodes; and areception component adapted for receiving, in response to the signallinginformation, an aggregated feedback report from a feedback aggregationserver separate from the downstream signalling distribution tree,wherein the aggregated feedback report is indicative of feedback reportsfrom the plurality of network access nodes related to the signallinginformation. The transmission component may be adapted for transmittingthe signalling information based on a PTM service of the networkenvironment.

According to another aspect of the invention, a network access node isproposed, which is adapted for handling PTM content transmissions in aPTM-enabled network environment. The network access node comprises areception component adapted for receiving signalling information relatedto a PTM content transmission from a PTM control node, wherein thesignalling information is received along a downstream signallingdistribution tree; a determination component adapted for determining afeedback aggregation server, wherein the feedback aggregation server isseparate from the downstream signalling distribution tree; and atransmission component adapted for transmitting a feedback reportrelated to the signalling information to the feedback aggregationserver.

According to a still further aspect of the invention, a feedbackaggregation server is proposed, which is adapted for a PTM-enablednetwork environment, in which signalling information related to a PTMcontent transmission is transmitted from a PTM control node along adownstream signalling distribution tree to a plurality of network accessnodes. The feedback aggregation server comprises a control componentadapted for receiving feedback reports responsive to the signallinginformation from a plurality of senders; an aggregation componentadapted for aggregating the received feedback reports into an aggregatedfeedback report; and a transmission component adapted for transmittingthe aggregated feedback report; wherein the feedback aggregation serveris separate from the downstream signalling distribution tree. Thefeedback aggregation server may be co-located with a network accessnode. Additionally or alternatively, the feedback aggregation server maybe associated with a PTM control node.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will further be described with referenceto exemplary embodiments illustrated in the figures, in which:

FIG. 1A schematically illustrates an embodiment of a PTM-enablednetwork;

FIG. 1B schematically illustrates an embodiment of a control multicastgroup in the network of FIG. 1A;

FIG. 1C schematically illustrates an embodiment of a sub-network offeedback aggregation servers for the PTM-enabled network of FIG. 1A;

FIG. 1D schematically illustrates a further embodiment of a PTM-enablednetwork with a sub-network of feedback aggregation servers;

FIG. 2 is a functional block diagram schematically illustrating anembodiment of an aggregation server;

FIG. 3 is a functional block diagram schematically illustrating anembodiment of a PTM control node;

FIG. 4 is a functional block diagram schematically illustrating anembodiment of a network access node;

FIG. 5 is a flow chart illustrating steps of a method embodiment ofoperating a feedback aggregation server;

FIG. 6 is a flow chart illustrating steps of a method embodiment forcontrolling PTM content transmissions;

FIG. 7 is a flow chart illustrating steps of a method embodiment ofoperating a network access node for handling PTM content transmissions;and

FIG. 8 is a sequence chart illustrating an embodiment of a signallingmessage flow related to a PTM content transmission.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth, such as specific networkarchitectures including particular network nodes, communicationtechniques etc., in order to provide a thorough understanding of thecurrent invention. It will be apparent to one skilled in the art thatthe current invention may be practised in other embodiments that departfrom these specific details. For example, the skilled artisan willappreciate that the current invention may be practised withcommunications networks different from the UMTS networks discussed belowto illustrate the present invention. The invention may be practised withany network in which PTM services for content transmissions areprovided. This may include any kind of wireless networks, for examplenetworks based on WLAN (Wireless Local Area Network). This may, however,also include wireline networks, for example any kind of IP-basednetworks.

Those skilled in the art will further appreciate that functionsexplained hereinbelow may be implemented using individual hardwarecircuitry, using software functioning in conjunction with a programmedmicroprocessor or a general purpose computer, using an applicationspecific integrated circuit (ASIC) and/or using one or more digitalsignal processors (DSPs). It will also be appreciated that while thecurrent invention is described as a method, it may also be embodied in acomputer processor and a memory coupled to a processor, wherein thememory is encoded with one or more programs that perform the methodsdisclosed herein when executed by the processor.

FIG. 1A illustrates an embodiment of a PTM-enabled network 100comprising a PTM control node 102 and a plurality of network accessnodes 104. The network 100 may be an UMTS LTE network, wherein the PTMcontrol node 102 is implemented in an edge gateway (EGW), for example anevolved GGSN or a BM-SC, and the network access nodes are represented byevolved nodeBs (eNBs). It is generally intended that the term “node”when used herein may be understood as designating a “functional node”,i.e. designating a particular set of functions, rather than a physicalnode. The functions need not necessarily be implemented on a singlephysical node. As an example, the functions of a BM-SC may not beimplemented on a dedicated standalone physical node, rather itsfunctions might be provided co-located with other nodes. In general, thefunctions of a PTM control node may be implemented distributed overseveral physical nodes.

Referring back to FIG. 1A, a signalling message 106 is distributed fromthe edge gateway 102 over intermediate nodes 108 and 110 to the accessnodes 104. The signalling 106 is intended for controlling a PTM contenttransmission. A service area (not shown) is associated with a PTMservice used for the PTM content transmission. Some or all of the accessnodes 104 belong to the service area. For example, the signallingmessage 106 may be an MBMS Session Start message for initiating an isMBMS multicast content transmission.

The signalling message 106 is distributed based on a PTM service,hereinafter referred to as a “PTM control service”, provided by thenetwork 100. The PTM control service is different from the PTM service(“PTM content service”) used for the actual PTM content transmission.The access nodes 104 are the recipients of the PTM control service,which may be, for example, an MBMS multicast service. The distributiontree of the PTM control service may comprise several hierarchy levels,which are represented in the example depicted in FIG. 1A by thedownstream nodes 108 and 110. As an example, the downstream nodes 108and 110 may be routers which act to transparently forward the signallingmessage 106 towards the evolved NodeBs 104.

In principle, any signalling related to a PTM content transmission maybe transported using the PTM control service. Assuming that the PTMcontent transmission is based on an MBMS service, in particular the MBMSSession Start, Session Stop and Session Update messages can betransported using an IP multicast group as the PTM control service. Thenetwork access nodes may be addressed within the signalling messages viaservice identifiers such as service area identifiers in MBMS. Theservice identifier is associated with a (potentially large) number ofnetwork access nodes 104. Vice versa, there may be multiple serviceidentifiers associated with each access node 104. On reception of thesignalling message 106 via a PTM control service, each of the nodes 104determines if the indicated service identifier corresponds to a serviceidentifier assigned to the node 104. If this is the case, the node 104may prepare for the indicated PTM content transmission. If this is notthe case, the node 104 may ignore (discard) the signalling message 106.

In one embodiment, some or all of the network access nodes of a(sub-)network may be members of a multicast group for the purpose ofdistributing signalling information related to the control of PTMcontent transmissions. Such a multicast group will be referred to as a“control multicast group” (CMG) hereinafter. A CMG for the network 100of FIG. 1A is illustrated in FIG. 1B, in which like reference numeralsdesignate like entities. The network components 102-110 of the network100 are included (as indicated by the oval line) in a CMG. As anexample, the CMG may be based on an IP multicast service, for example anMBMS service. The EGW forms the root and the access nodes form theleaves of the CMG distribution tree. In this way, any signalling relatedto different PTM content transmissions controlled by the node 102 andwith service areas including at least some of the access nodes 104 maybe distributed using the CMG depicted in FIG. 1B.

In large networks, it may be advisable to configure several separateCMGs. As an example, several CMGs might cover separate geographicalareas. In case the service area of a PTM content service extends overseveral CMG areas, a PTM control node such as the edge gateway 102 inFIG. 1A, 1B has to initiate several CMGs. The service areas of differentCMGs may be chosen according to other, non-geographical conditions. Forinstance, network access nodes with similar technical properties may begrouped accordingly in CMGs. As an example, all GSM access nodes, UMTSaccess nodes, and LTE access nodes may correspondingly be groupedtogether.

Each signalling message may contain at least one identifier unique for aCMG, e.g. a TMGI (Temporary Mobile Group Identity, see the 3GPP TS23.246). Several service identifiers may be transported which areassociated with different (e.g., localized) CMGs. In addition, one ormore addresses of particular network access nodes may be included in asignalling message. The multicast group used for transporting the PTMcontent transmission (content or transport level multicast group, TLMG)has a separate multicast address, which is maintained by the edgegateway 102 (or a BM-SC not depicted in FIGS. 1A, 1B). The TLMG addressis propagated down to the access nodes 104 using an appropriate CMG.Thus, a signalling message may contain the TLMG address for the PTMcontent transmission.

FIG. 1C schematically illustrates an embodiment of a mechanism forpropagating signalling feedback for the network 100 of FIG. 1A. Again,like reference numerals designate like entities.

Each of the network access nodes 104 may determine if a receivedsignalling message has to be processed or not based on informationreceived in the signalling message. For example, a service identifiermay be provided by the signalling. In case the service identifier is onewhich is also assigned to the access node, the node will provide afeedback to the PTM control node. Additionally or alternatively, thereceived signalling message may contain a network address of the accessnode, such that the node is directly addressed as being involved in thePTM content transmission.

To ensure a reliable and fast PTM content transmission, the access nodes104 (all of which are assumed in FIG. 1C to belong to the service areaof the content transmission) may be adapted to provide a feedback reporttowards the PTM control node 102 in response to the signalling message106 (FIG. 1A). Apart from a direct response to a received signallingmessage, the terms “feedback”, “feedback report” or “feedback message”herein are intended to comprise any kind of information, which isrelated to signalling (which is in turn related to a PTM contenttransmission) and which is transmitted from the network access nodes“towards” (i.e., via one or more aggregation servers) the PTM controlnode.

Such a feedback may therefore not only include feedback reports sent indirect response to the reception of signalling information. Rather, afeedback may additionally or alternatively include, e.g., a reportindicating a successful allocation of resources or a status report. Sucha report may be transmitted towards the PTM control node on a regularbasis (timer-based “heartbeat” status reporting). Status reports mayalso be triggered by particular events, for instance a change ofavailable or used resources. As an example, a PTM bearer may have to bedropped during an ongoing content transmission due to a resourceshortage. A feedback may also be triggered based on thresholds. As anexample, the number of users served by a particular network access nodemay reach a particular threshold. As another example, the amount ofavailable resources may fall below a predetermined threshold.

A signalling message may contain feedback control information such as afeedback request indicator. In case the indicator is set, this maycommand the network access node to send a feedback or to send aparticular kind of feedback. In the absence of specific feedback controlinformation from the PTM control node, the network access node may usedefault feedback control parameters in this respect.

As shown in FIG. 1C, the network access nodes 104 do not send theirfeedback directly to the PTM control node 102, but to feedbackaggregation servers 112. These nodes are disposed separately from thesignalling distribution tree depicted by the arrows (“MSG”) in FIG. 1A,i.e. they are excluded from the signalling distribution tree. Theaggregation servers are adapted for being disposed separately from thesignalling distribution tree. For example, they may be specificallyadapted to receive and accept feedback messages, e.g. acknowledgementmessages, without being the originator of the signalling messages, inresponse to which the feedback messages are transmitted. As an example,a feedback aggregation server may be adapted to accept feedback messagesindicating one or more particular network access nodes as the sources ofthe feedback messages, or indicating a particular PTM control node asthe final destination of the feedback.

Each of the feedback aggregation servers collects the feedback receivedfrom multiple access nodes 104 and provides an aggregated feedbacktowards the PTM control node 102. In the example illustrated in FIG. 1C,the aggregated feedback information of the aggregation servers 112 isnot send directly to the control node 102, but is propagated to ahigher-level aggregation server 114, which aggregates the aggregatedfeedback information again, such that a two-fold aggregated feedbackinformation is eventually forwarded to the PTM control 102.

Within a multi-level hierarchy, each feedback aggregation servercollects the feedback information from the lower level and forwards anaggregated feedback report to the next higher level. In otherembodiments, a one-level hierarchy of aggregation servers may beutilized, for example in smaller networks and/or in case PTM contenttransmissions comprise a small service area only. For example, severalfeedback aggregation servers may be provided, which directly receivefeedback from the network access nodes and which directly provideaggregated feedback information to the PTM control node. In anotherembodiment, only a single feedback aggregation server may be employed.Apart from the hierarchical structure depicted in FIG. 1C, thesub-network of feedback aggregation servers may be organized accordingto another topology. For example, a flat topology may be applied whereineach server receives feedback reports directly from the access nodes andtransmits its aggregated feedback report directly to the PTM controlnode. The sub-network of feedback aggregation nodes may be organizedindependently, i.e. according to a completely different topology, fromthe sub-network formed by the PTM control node, the network access nodesand possibly further nodes such as routers.

In general, feedback aggregation servers may be co-located with othernetwork nodes or may be provided as dedicated stand-alone entities. InFIG. 1C it is illustrated that the feedback aggregation servers 112, 114are co-located with the routing nodes 110 and 108. In other embodiments,one or more of the aggregation servers may be co-located with networkaccess nodes.

This is illustrated in FIG. 1D, in which a control multicast group mayinclude an edge gateway 120 as root and network access nodes 121-125 asleaves. Two lower-level aggregation servers 126, 127 are provided foraggregating the feedback from the nodes 121-125. The servers 126 and 127are co-located with the access nodes 122 and 123, respectively. Forexample, the access node 122 and the aggregation server 126 may beimplemented on the same physical node. These physical nodes may receiveassignment information which indicate an assignment of an aggregationfunctionality to the node, such that, e.g., the node hosting the networkaccess node 122 additionally takes on the role of the feedbackaggregation server 126.

The access nodes 121 and 122 are adapted to direct their feedbackreports to the feedback aggregation server 126, whereas the access nodes123, 124, 125 direct their feedback to the aggregation server 127. Forexample, each of the access nodes 121-125 may have a default aggregationserver associated therewith, namely one of the servers 126 and 127.

The lower-level aggregation servers 126, 127 transmit their aggregatedfeedback reports to the high-level feedback aggregation server 128,which in turn transmits its two-fold aggregated feedback report to thePTM control node 120. Note that the hierarchy of aggregation servers(the “uplink hierarchy”) is independent from the hierarchy (the“downlink hierarchy”) in the signalling distribution tree from the root120 towards the leaves 121-125. For example, in another embodiment theaggregation server 126 may provide its aggregated feedback report to theaggregation server 127 instead of the server 128. The server 127 maythen provide an aggregated feedback report, which is based on thefeedback from the access nodes 123-125 and the aggregated feedbackreport from the server 126 to the aggregation server 128. In stillanother embodiment, the server 128 may be omitted, and the aggregationserver 127 may report directly to the PTM control node 120.

In still further embodiments, a PTM control node may have a co-locatedfeedback aggregation server. Co-located nodes may be implemented on thesame hardware entity with either dedicated or shared network interfaces.As an example, in a hierarchically organized sub-network of aggregationservers the aggregation server of highest level, i.e. next to the PTMcontrol node, may be implemented on a common hardware platform with thePTM control node but with a processing hardware separate from that ofthe PTM control node to achieve the advantage of unburden the PTMcontrol node from the processing of a massive amount of feedbackinformation.

Referring back to FIG. 1C, the PTM control node 102 analyzes thereceived aggregated feedback report. A feedback report contained in afeedback message transmitted from a network access node may compriseonly a minimum of information. For example, the feedback may compriseonly the source address of the sender. Such a feedback report may forexample serve as a “still alive” message, which contributes to ensuringthe reliability of the ongoing content transmission. On the other hand,a feedback report may include information on the reception time of asignalling message, information on the number and identity of receiverunits in the cell served by the network access node, information relatedto the available resources or resource usage for the contenttransmission and/or other services in relation to the access node, etc.

As the PTM control node 102 forms the root of the feedback aggregationtree, it depends on the details of the feedback aggregation scheme whichof the feedback information provided by the network access nodes willarrive at the control node. The control node 102 may, e.g., determine,based on the aggregated feedback information, which of the networkaccess nodes 104 have responded to the signalling message. In case oneor more access nodes 104 have not responded, these nodes may not belisted in the received aggregated feedback status information. Then thetransmission of the signalling message may have to be repeated to ensurereliability for the controlled PTM content transmission.

The access node may be assigned the functionality (the “role”) of afeedback aggregation server by administration of the network operator.Alternatively, a network node may receive an assignment informationassociated with, e.g., a signalling message related to a PTM contenttransmission, for example an MBMS Session Start message. Additionally oralternatively, dedicated feedback aggregation servers can be provided inthe network. Multiple feedback aggregation servers may form a pool.

One or more feedback aggregation servers may be associated fixedly (e.g.via administration) with a PTM control node. As an example, in FIG. 1C,the aggregation servers 112 and 114 may be associated with the PTMcontrol node 102 such that these particular aggregation servers serve toaggregate the feedback from the network access nodes 104 controlled bythe control node 102. Additionally or alternatively, feedbackaggregation servers may be assigned to a particular signalling contextrelated to a PTM content transmission on request of the PTM controlnode. These and further mechanisms may be utilized to distribute theload over the aggregation servers available in the network and to avoidoverload.

Referring back to FIG. 1A, the signalling message 106 may denominate theone or more feedback aggregation servers 112 to be used by the networkaccess nodes 104 for feedback. Additionally or alternatively, an accessnode 104 may have one or more default aggregation servers. The provisionof several aggregation servers to a network access node may be useful toensure reliability, for example for redundancy reasons. In case ofseveral available feedback aggregation servers, the access node 104 mayapply an appropriate prescription to decide on the aggregation server touse, wherein the prescription ensures, e.g., load balancing aspects. Forexample, the access node 104 may randomly choose one of the availableaggregation servers 112. Similar mechanisms may be applied for thelow-level aggregation servers 112 to enable them identifying andselecting the high-level aggregation server 114.

The aggregation servers 112 may be made available to the access nodes104 by providing, e.g., an IP-address or a logical host name. In caselogical host names are provided to the access nodes 104, these may haveto be resolved by a DNS (Domain Name Service) server. The (resolved) IPaddress may be an IP multicast or IP anycast address. Such an addressmay be associated with multiple feedback aggregation servers. Forexample, the IP address may designate a pool of aggregation servers 112,from which a particular aggregation server is chosen according to aprescription taking into account, e.g., load balancing aspects.

In FIGS. 1A-1D it is shown that the functionality of a PTM control nodeis implemented on an edge gateway. In principle, the functionality ofthe PTM control node may be implemented on a BM-SC (in an MBMS scenario)or on an edge gateway or both. In some embodiments it may be preferredto provide the PTM control node functionality in the BM-SC, inparticular if a mapping of MBMS service areas and access nodes ismaintained in the BM-SC.

FIG. 2 schematically illustrates an embodiment of a feedback aggregationserver 200 which may for example be an implementation of the aggregationservers 112 or 114 of FIG. 1C. The aggregation server 200 is adapted fora PTM-enabled network environment, in which signalling informationrelated to a PTM content transmission is transmitted from a PTM controlnode along a downstream signalling distribution tree to a plurality ofnetwork access nodes. For example, the aggregation server 200 may beadapted for the network 100 of FIG. 1.

The aggregation server 200 comprises a reception component adapted forreceiving feedback reports responsive to the signalling information froma plurality of senders. The feedback information may be received, e.g.,from multiple access nodes. The reception component identifies theincoming information and provides the received feedback messages,acknowledgements, etc. to an aggregation component 204 which is adaptedfor aggregating the received feedback information into an aggregatedfeedback report. For example, the component 204 may buffer the feedbackreports for a predetermined period of time before compiling anaggregated feedback report. Further, the aggregation component mayextract particular information from the received feedback reports. Forexample, the component 204 may only extract the source addresses fromthe received feedback messages, e.g. the addresses of the sending accessnodes. The aggregation component may then construct the aggregatedfeedback information from the extracted information.

The aggregation component 204 provides the aggregated feedbackinformation to a transmission component 206 which is adapted fortransmitting the aggregated feedback report. To this end, the component206 may determine an address of either another aggregation server in anext-higher hierarchy level or the address of the PTM control node.

The aggregation server 200 may be co-located with, e.g., a networkaccess node. In this case, the components 202, 204 and 206 may beimplemented on the same hardware as the components of the network accessnode. This particular access node may then provide its feedback byinternal messaging to the reception component 202. Further, theaggregation server 200 may be associated with a particular PTM controlnode, e.g. by storing the address of the PTM control node in a storagecomponent of the aggregation server 200 via an administration interface.In this case, the component 206 might simply insert the stored addressinto a message including the aggregated feedback information.

FIG. 3 schematically illustrates an embodiment of a PTM control node 300which may for example be an implementation of the control node 102 ofFIG. 1B. The control node 300 may be implemented on a BM-SC of an UMTSor LTE network or may be implemented on an edge gateway, e.g. an evolvedGGSN, of such a network. The functionality of the PTM control node 300may also be implemented distributedly on a BM-SC and an edge gateway.

The PTM control node 300 is adapted for controlling PTM contenttransmissions in a PTM-enabled network environment, e.g. in the network100 in FIG. 1. The PTM control node 300 comprises a transmissioncomponent 302 which is adapted for transmitting signalling informationrelated to a PTM content transmission along a downstream signallingdistribution tree to a plurality of network access nodes. As an example,the component 302 may prepare and transmit MBMS session relatedsignalling messages such as Session Start and Session Stop messages. Thetransmission component may initiate one or more PTM control services inthis regard.

The control node 300 further comprises a reception component 304 whichis adapted for receiving, in response to the signalling information, anaggregated feedback report from a feedback aggregation server separatefrom the downstream signalling distribution tree, such as theaggregation server 200 of FIG. 2 or server 114 of FIG. 1C. Theaggregated feedback report is indicative of feedback reports from theplurality of network access nodes related to the signalling information.The aggregated feedback information may influence further signallingrelated to the PTM content transmission. For example, an analysis of theaggregated feedback information may trigger a repetition of thesignalling message transmission at the component 302.

FIG. 4 schematically illustrates an embodiment of a network access node400 which is adapted for handling PTM content transmissions in aPTM-enabled network environment. The access node 400 may for example bea representation of the nodes 104 in FIGS. 1A, 1B, 1C or 121-125 in FIG.1D.

The access node 400 comprises a reception component 402 which is adaptedfor receiving signalling information related to a PTM contenttransmission from a PTM control node (for example the node 102 of FIG.1), wherein the signalling information is received along a downstreamsignalling distribution tree. In response to the received signallinginformation, the access node 400 may provide a feedback report towardsthe PTM control node, which may at least indicate an identity of theaccess node.

The reception component 402 may trigger a transmission component 404,which is adapted for transmitting a feedback report related to thesignalling information to the feedback aggregation server. The receptioncomponent 402 may either trigger the transmission component 404 indirect response to a received signalling information, and/or may triggerthe component 404 on a periodical basis or in response to furtherevents.

The transmission component 404 may trigger a determination component404, which is adapted for determining a feedback aggregation server,wherein the feedback aggregation server is separate from the downstreamsignalling distribution tree. The determination component 404 may forexample be adapted to read the address of a default aggregation serverfrom a storage component of the access node 400 (not shown) or toextract the address of an aggregation server from a buffered signallingmessage. In case that several addresses are available to the addresscomponent 404, an implemented decision algorithm decides on theparticular address to use.

The determination component 406 provides the determined address of thefeedback aggregation server to the transmission component 404, which mayconstruct a feedback message with the determined address of the feedbackaggregation node as the destination address and a network address of theaccess node 400 as the source address, such that the source addressserves as the identity indication for the access node 400. In otherembodiments, further information may be inserted into the feedbackreport, such as an indication of the signalling message and/or PTMcontent transmission, to which the feedback is related. The transmissioncomponent 406 then transmits the feedback report to the address of thefeedback aggregation server.

The reception component 402 may, on reception of the signallinginformation, further trigger a content-handling component 408, which isadapted for handling the content distributed by the PTM contenttransmission. In particular, the component 408 is adapted for receivingand forwarding the content to multiple recipients. The trigger from thereception component 402 may, for example, serve to prepare the receptionof the PTM content transmission in the component 408. In other cases,the trigger may lead to a re-configuration of resources controlled bythe component 408 during an ongoing PTM content transmission or when thecontent transmission is stopped.

FIG. 5 schematically illustrates the steps of an embodiment of a method500 of operating a feedback aggregation server, for example the nodes112 or 114 in FIG. 1C or the node 200 of FIG. 2, in a PTM-enablednetwork environment such as the network 100 in FIG. 1C, in whichsignalling information related to a PTM content transmission istransmitted from a PTM control node along a downstream signallingdistribution tree to a plurality of network access nodes.

In step 502, the method is triggered, for example, by a timer, by acounter or by the reception of feedback reports responsive to thesignalling information from a plurality of senders. In step 504, thereceived feedback reports are aggregated into an aggregated feedbackreport; for example, the source addresses of each of the receivedfeedback reports may be extracted and collected in a list. In step 506,the aggregated feedback information is transmitted, for instance to aPTM control node or to another aggregation server. In step 508, themethod ends with the feedback aggregation server being idle and waitingfor further feedback to be received.

FIG. 6 schematically illustrates the steps of an embodiment of a method600 for controlling PTM content transmissions in a PTM-enabled networkenvironment. The method may be performed in a PTM control node, forexample the edge gateway in 102 in FIGS. 1B, 1C or the node 300 in FIG.3.

The method is triggered in step 602; for example, a PTM contenttransmission may be queued for processing. In step 604, signallinginformation related to the PTM content transmission is transmitted alonga downstream signalling distribution tree to a plurality of networkaccess nodes. The signalling information may be related to the start, areconfiguration or the end of the content transmission. In step 606, anaggregated feedback information is received in response to thesignalling information from a feedback aggregation server separate fromthe downstream signalling distribution tree. The aggregated feedbackinformation is indicative of feedback reports from the plurality ofnetwork access nodes related to the signalling information.

In step 608, some further control processing related to the PTM contenttransmission is performed, which is based on the received aggregatedfeedback information. For example, a repetition of the signallingtransmission may be queued at least to some access nodes which missedthe first transmission. The method ends in step 610 with the PTM controlnode being idle and waiting for further triggering events.

FIG. 7 schematically illustrates the steps of an embodiment of a method700 of operating a network access node, for example the nodes 104 inFIG. 1B or node 400 of FIG. 4, for handling PTM content transmissions ina PTM-enabled network environment.

The method is triggered in step 702 by the reception of signallinginformation related to a PTM content transmission from a PTM controlnode. The method may also be triggered, e.g., by the expiry of a timer.The signalling information is received along a downstream signallingdistribution tree with the PTM control node forming the root of thetree.

In step 704, a feedback aggregation server is determined, wherein thefeedback aggregation server is separate from the downstream signallingdistribution tree. An address of the server may be determined, e.g., adefault address or an address received with the signalling information.In step 706, a feedback report related to the signalling information istransmitted to the feedback aggregation server. In step 708, thehandling of the PTM content transmission is triggered. For example, thereceived signalling information may be related to the start of a PTMcontent transmission. The step 708 may then trigger a preparation of thereception of the PTM content transmission in the network access node, aswell as its forwarding to the intended recipients of the content. Forexample, appropriate resources may be allocated. The method ends in step710.

FIG. 8 schematically illustrates an embodiment of a message sequence 800in an LTE network, which involves a number of network access nodes(evolved NodeBs) 802, 803, 804, an edge gateway (access gateway, AGW)806 and an evolved BM-SC 808. A PTM control node functionality isimplemented distributedly on the nodes 806 and 808.

In step 1), the evolved BM-SC 808 transmits an MBMS session startmessage to the edge gateway 806 in order to trigger the establishment ofan MBMS distribution plane for an MBMS content transmission. The messagecomprises a TMGI identifying the user level group, one or more MBMSservice area identifiers, and a user-level multicast group address. Inaddition, one or more flow IDs may be included in the session startmessage, for example if several traffic flows have to be multiplexed onthe multicast group. As an example, several UDP (User Datagram Protocol)destination ports may be indicated. An indication of one or more(localized) CMGs may be included. The message may further contain afeedback request indication as described above.

In step 2), the edge gateway acknowledges reception of the MBMS sessionstart message. In step 3), the edge gateway 806 acts as a PTM controlnode and determines the CMG(s) to use for distribution of the MBMSSession Start message. The CMG(s) may have been indicated in the messagein step 1), or the edge gateway 806 may derive the CMGs from thereceived MBMS service area identifier(s). A derivation algorithm may beprovided to the edge gateway 804 in this respect, which may scan acorresponding mapping table. In step 4), the MBMS Session Start messageincluding the service area identifier(s) is then propagated along thedownstream signalling distribution tree towards the network access nodes802, 803, 804 using one or more MBMS multicast services associated withthe indicated or derived CMGs. No PTP connections need to be initiatedfor signalling purposes. However, the edge gateway 806 may set upunicast connections to one or few access nodes for signalling purposes,e.g. if these access nodes are not member in the CMG(s).

In the example illustrated in FIG. 8, it is assumed that all evolvedNodeBs 802-804 receive the MBMS Session Start message. In case a networkaccess node does not belong to the indicated MBMS service area(s), itmay discard the signalling message. This is the case for node 804. Theservice area IDs may have been assigned to the access nodes via anadministrative action. In step 5), the access nodes 802 and 803 join theTLMG, as they have one of the service areas indicated in the SessionStart message assigned with it. For example, they may send a querymessage to the TLMG group, e.g. an IGMP (IP Group Management Protocol)message.

In step 6), the BM-SC 808 starts to transmit content data to the TLMG.The edge gateway 806 encapsulates the TLMG traffic and tunnels it to thenetwork access nodes 802 and 803. The TLMG indication is used forrouting in the core network. If present, a flow-ID may be added as atunnelling header. In case the flow-ID is to be used in step 6), it hasto be signalled in step 3). In step 7), the network access nodes 802 and803 receive the content and transmit the content utilizing appropriateradio bearers chosen according to the TLMG and the optional flow-ID. Thesteps 6) and 7) thus constitute a PTM content transmission.

The techniques proposed herein allow a reduction of the processingburden of PTM control nodes, such as a BM-SC in an MBMS framework or anetwork node acting as an edge gateway, when controlling PTM contenttransmissions. For example, transmitting-related signalling informationutilizing a PTM service of a network environment allows avoiding theprocessing overhead associated with setting up a possibly large numberof parallel unicast connections. The concept of control multicast groups(CMGs) is based on defining multicast groups which may be used forsignalling purposes only. One or few CMGS only may be required pernetwork, as the service area of a CMG can be larger or smaller than theservice area of a PTM content transmission.

The concept of feedback aggregation by using an aggregation server or anetwork of aggregation servers, which may be organized hierarchicallyand may be separated from the network structure used for the signalling(and the content transmission), allows to reduce the burden of the PTMcontrol node with processing a possibly massive amount of feedbackinformation. The PTM control node typically will receive only one or fewaggregated feedback messages. A sub-network of aggregation servers maybe dynamically adapted to the requirements of content transmissionsmomentarily performed in the network environment.

While the current invention has been described in relation to itspreferred embodiments, it is to be understood that this disclosure isfor illustrative purposes only. Accordingly, it is intended that theinvention be limited only by the scope of the claims appended hereto.

1. A method for controlling point-to-multipoint (PTM) contenttransmissions in a PTM-enabled network environment, the methodcomprising the steps of: transmitting signalling information related toa PTM content transmission along a downstream signalling distributiontree to a plurality of network access nodes, wherein the signallinginformation indicates a multicast address for use by the network accessnodes for transmitting feedback reports; and receiving, in response tothe signalling information, an aggregated feedback report from afeedback aggregation server separate from the downstream signallingdistribution tree, wherein the aggregated feedback report is indicativeof feedback reports from the plurality of network access nodes relatedto the signalling information.
 2. The method according to claim 1,wherein the multicast address is associated with multiple feedbackaggregation servers.
 3. The method according to claim 1, comprising thefurther step of repeating, based on an evaluation of the receivedaggregated feedback report, the transmission of the signallinginformation.
 4. The method according to claim 3, wherein the repeatedtransmission of the signalling information is performed based onpoint-to-point service of the network environment.
 5. The methodaccording to claim 1, wherein the signalling information comprises afeedback request indication.
 6. The method according to claim 1, whereinthe signalling information is transmitted using a PTM service of thenetwork environment.
 7. A method of operating a network access node forhandling point-to-multipoint (PTM) content transmissions in aPTM-enabled network environment, the method comprising the steps of:receiving signalling information related to a PTM content transmissionfrom a PTM control node, wherein the signalling information is receivedalong a downstream signalling distribution tree and the signalinginformation indicates a multicast address; determining a feedbackaggregation server separate from the downstream signalling distributiontree according to the multicast address; and transmitting a feedbackreport related to the signalling information to the feedback aggregationserver using the multicast address.
 8. The method according to claim 7,wherein the multicast address is associated with multiple feedbackaggregation servers.
 9. The method according to claim 7, wherein anaddress of the feedback aggregation server is different from an addressof the PTM control f)ode.
 10. The method according to claim 7, whereinthe feedback report comprises at least one of an acknowledgement ofreceived signalling information, an indication of a result of a processtriggered by the received signalling information and status informationrelated to the PTM content transmission.
 11. The method according toclaim 7, wherein the signalling information is received based on a firstPTM service of the network environment.
 12. The method according toclaim 11, wherein the received signalling information comprises aservice identifier, and the method comprises, based on the serviceidentifier, the step of identifying, a second PTM service of the networkenvironment for the PTM content transmission.
 13. A method of operatinga feedback aggregation server, in a point-to-multipoint (PTM) enablednetwork environment, in which signalling information related to a PTMcontent transmission is transmitted from a PTM control node along a downstream signalling distribution tree to a plurality of network accessnodes and wherein the signaling information indicates a multicastaddress for use by the network access nodes for transmitting feedbackreports, the method comprising the steps of: receiving feedback reportsresponsive to the signalling information from a plurality of senders;aggregating the received feedback reports into an aggregated feedbackreport; and transmitting the aggregated feedback report wherein thefeedback aggregation server is separate from the downstream signalingdistribution tree.
 14. The method according to claim 13, furthercomprising, receiving an indication of at least one of the PTM controlnode and a higher-level feedback aggregation server as a destination forthe aggregated feedback report.
 15. The method according to claim 14,wherein the indication comprises an indication of a multicast addressassociated with multiple higher-level feedback aggregation servers. 16.The method according to claim 13, comprising the step of selecting oneserver from a list of higher-level feedback aggregation servers.
 17. Themethod according to claim 13 comprising the further step of receivingassignment information indicating an assignment of an aggregation serverfunctionality to the receiving node.
 18. The method according to claim13 wherein the aggregated feedback report is transmitted atpredetermined time intervals.
 19. The method according to claim 13,wherein the plurality of senders comprise at least one of one or more ofthe plurality of network access nodes and one or more lower-levelfeedback aggregation servers. 20-21. (canceled)
 22. A PTM control nodeadapted for controlling point-to-multipoint (PTM) content transmissionsin a PTM-enabled network environment, the PTM control node comprising: atransmission component adapted for transmitting signaling informationrelated to a PTM content transmission along a downstream signallingdistribution tree to a plurality of network access nodes, wherein thesignalling information indicates a multicast address for use by thenetwork access nodes for transmitting feedback reports; and a receptioncomponent adapted for receiving, in response to the signallinginformation, an aggregated feedback report from a feedback aggregationserver separate from the downstream signaling distribution tree, whereinthe aggregated feedback report is indicative of feedback reports fromthe plurality of network access nodes related to the signallinginformation.
 23. The PTM control node according to claim 22, wherein thetransmission component is adapted for transmitting the signalinginformation based on a PTM service of the network environment.
 24. Anetwork access node adapted handling point-to-multipoint (PTM) contenttransmissions in a PTM-enabled network environment, the network accessnode comprising: a reception component adapted for receiving signallinginformation related to a PTM content transmission from a PTM controlmodem, wherein the signalling information is received along a downstreamsignalling distribution tree and the signalling information indicates amulticast address;. a determination component adapted for determining afeedback aggregation server separate from the downstream signalingdistribution tree according to the multicast address; and a transmissioncomponent adapted for transmitting a feedback report related to thesignalling information to the feedback aggregation server using themulticast address.
 25. A feedback aggregation server adapted for aPTM-enabled network environment, in which signaling information relatedto a PTM content transmission is transmitted from a PTM control nodealong a downstream signalling distribution tree to a plurality ofnetwork access nodes and the signalling information indicates amulticast address for use by the network access nodes for transmittingfeedback reports, the feedback aggregation server comprising: areception component adapted for receiving feedback reports responsive tothe signalling information from a plurality of senders; an aggregationcomponent adapted for aggregating the received feedback reports into anaggregated feedback report; and a transmission component adapted fortransmitting the aggregated feedback report, wherein the feedbackaggregation server is separate from the downstream signalingdistribution tree.
 26. The feedback aggregation server according toclaim 25, wherein the feedback aggregation server is co-located with anetwork access node.
 27. The feedback aggregation server according toclaim 25, wherein the feedback aggregation server is associated with aPTM control node.